1. Field of the Invention
The present invention relates to a washing machine and, more particularly, to a fully-automatic washing machine adapted to automatically perform the steps of washing, rinsing and drying.
2. Description of the Prior Art
In general, fully automatic washing machines proposed and used hitherto can be sorted into two types: namely, pulsator type machine in which a rotary blade unit is rotated in the washing and rinsing steps at a comparatively high speed in one and the other directions with a comparatively long interval of switching of rotation direction, and agitator type machine in which the rotary blade unit is rotated in the washing and rinsing steps at a comparatively low speed in one and the other direction at a comparatively low speed in one and the other directions with a comparatively short interval of switching of rotation direction.
More specifically, in the pulsator type washing machine, the direction of rotation of the rotary blade unit is switched at a long interval such that the rotation of the rotary blade unit is stopped for 3 seconds after a continuous forward rotation for 27 seconds and followed by a continuous backward rotation for 27 seconds. The rotation speed of each of forward and backward rotation is as high as 400 rpm. For these reasons, the pulsation type washing machines usually suffer the following problems.
(1) The wash is liable to be damaged because it is held for long time in contact with the rotary blade unit which rotates at a high speed.
(2) The wash, such as clothes or the like, are made to entangle with one another heavily so that it is often necessary to unfasten or loosen the clothes or the like before turning to the rinsing step or washing step.
(3) As the drying step is started following the rinsing step, an eccessively large unbalance of force is produced due to the entanglement of clothes which often results in an inconveniet stopping of the operation of the washing/drying machine.
(4) The entanglement of clothes results in an imperfect washing of the entangled portions by causing to cause uneven washing and rinsing.
The entanglement and the damage of clothes are not so great in the agitator type washing machines because in this case the rotary blade unit is rotated in the forward and backward directions within an angle less than 360.degree. at a low speed. The agitator type washing machines, however, have the following drawbacks.
(1) The washing power is so limited that the contaminants of the clothes cannot be removed perfectly when the washing is made with cold water, i.e. unless warm water is used.
(2) A complicated mechanism is necessary for reciprocatingly rotating the rotary blade unit within the angle less than 360.degree.. This complicated mechanism seriously lowers the productivity of the washing machine.
The present inventors have conducted a test with a washing machine in which the rotary blade unit has a greater diameter than the rotary blade unit of conventionally used pulsator type washing machine and a cylindrical member is attached to the rotary blade unit. The rotary blade unit was rotated in forward and backward directions at a speed lower than that in the conventionally used pulsator type washing machine. This washing machine proved to be able to overcome the problems such as entanglement and damaging of the clothes, but still suffered a problem that the wash such as clothes is inconveniently caught around the cylindrical member.